Wastewater or “gray water” from food preparation facilities typically comprises grease, oil, fat and surfactants, collectively the “organic phase”, and water which may also contain food solids, the “aqueous phase”. The aqueous phase of wastewater can be easily passed through wastewater piping and treated by wastewater treatment systems, however, if the organic phase is allowed to enter sewer lines and wastewater treatment systems, it can form blockages in the wastewater piping, primary treatment systems, publicly owned treatment works (POTWs) and leach fields.
To reduce this problem and capture the organic phase before it enters wastewater collection and treatment piping, grease traps have traditionally been used in food preparation and processing facilities, such as restaurants, schools, hospitals, processing plants and the like. Grease traps are large cavities or tanks in wastewater piping systems that collect the organic phase, which is typically mixed with the aqueous phase, as it leaves the food preparation facilities but before the wastewater enters a wastewater treatment system. Grease traps allow the organic phase to separate out of The aqueous phase and float to the surface where the organic phase can be held or trapped until it can be collected and disposed.
The organic phase has a specific gravity that is less than the specific gravity of water. Accordingly, given sufficient time, the organic phase will float on the aqueous phase. When the organic phase is collected in a grease trap, some of the organic phase will be in or on substances that have a higher specific gravity. This can cause some of the organic phase to be suspended in the wastewater as suspended solids. Accordingly, the organic phase cannot simply be skimmed off the surface of the aqueous phase present in the grease trap. In addition, the cleaning of a grease trap causes violent mixing of the organic phase and the aqueous phase thereby distributing the organic phase throughout the aqueous phase. When the aqueous phase layer is pumped through the organic phase layer by the disposal truck, the aqueous phase and the organic phase are violently mixed to form organic/aqueous emulsions in the aqueous phase. Accordingly, the aqueous phase cannot simply be disposed of into the sewer lines due to the organic phase contained in the emulsions dispersed throughout the aqueous phase.
The size of the grease trap can vary depending on the amount of wastewater that passes through the trap and the amount of organic phase present in the wastewater. However, the grease traps used in typical food preparation facilities can be from about 1,000 to 2,000 gallons or more. Typically, the organic phase comprises only 10 to 50 percent of the total volume of the grease trap at the time of cleaning while the aqueous phase accounts for 50 to 90 percent of the volume of the grease trap. As such, a significant amount of the waste liquids and solids transported to the disposal site is the aqueous phase, and the hydrophilic solids residing in the aqueous phase, even though the aqueous phase does not pose any concerns to wastewater treatment systems if the organic/aqueous emulsions can be eliminated from it. Accordingly, traditional systems significantly increase the transportation costs and the energy required in typical disposal processes.
The present invention has been developed in view of the foregoing and to remedy other deficiencies of the prior art.